1. Field of the Invention
The present invention relates generally to converter circuits.
2. Background Art
In multi-band transmitters, baseband to radio frequency (RF) stages of the transmitter are designed as differential circuits for several reasons, including reducing common mode noise, cascading the gain stage without multiple bias elements, and allowing higher output signal swing. As a result, differential to single-ended signal conversion is required at the output stage.
Conventionally, differential to single-ended signal conversion at the output stage is performed using transformers. However, because each of the transformers needs to be optimized according to a respective frequency band, the reuse of transformers across frequency bands is precluded and a separate transformer is required for each band supported by the transmitter. The transmitter area thus tends to be very large. Further, because transformers are generally not integration-friendly, the implementation of the transmitter as a monolithic chip is significantly complicated.
There is a need therefore for improved differential to single-ended converters which are small in area and integration-friendly.
The present invention will be described with reference to the accompanying drawings. Generally, the drawing in which an element first appears is typically indicated by the leftmost digit(s) in the corresponding reference number.